1. Field of the Invention
The present invention relates to a silicon carbide sintered body and a method of manufacturing the same.
2. Description of the Prior Art
A silicon carbide sintered body has good oxidation resistance, corrosion resistance, thermal shock resistance, and mechanical strength, and has been studied for use as a high-temperature structural material for a gas turbine part, high-temperature heat exchanger, and the like.
Since silicon carbide powder as a raw material is hard to sinter, it has been sintered by a compression sintering process. However, in order to obtain a sintered body of a complex shape and to simplify a manufacturing process, an ambient pressure sintering process using a sintering assistant, e.g., boron, has been studied (for example, Japanese Patent Disclosure Nos. 50-78609 and 51-148712). With the ambient pressure sintering process, a sintered body of a complex shape can be manufactured in high yields. However, although boron contributes to densifying of the sintered body, it also causes a decrease in high-temperature mechanical strength of the sintered body. A carbon-containing oxygen scavenger, which is used for removing oxygen in the silicon carbide powder, plays an important role in densifying of the sintered body, but reduces the oxidation resistance of the sintered body.
For this reason, attempts have been made to improve the characteristics of the silicon carbide sintered body by decreasing the amount of boron added. For example, in a method described in Japanese Patent Disclosure No. 60-186467, a boron carbide powder having a large specific surface area is used as a boron source to reduce the amount of boron. Japanese Patent Disclosure No. 60-246263 describes a method wherein polyphenyl boron is used as boron and carbon sources.
As described above, although some methods associated with the ambient pressure sintering process for a silicon carbide sintered body have been proposed, silicon carbide sintered bodies obtained by these conventional methods are unsatisfactory in terms of high-temperature mechanical strength, oxidation resistance, and corrosion resistance.